Method and apparatus for absorbing mechanical shock

ABSTRACT

A method and apparatus for absorbing mechanical shock is disclosed. The apparatus comprises a pressure cylinder forming a working chamber having first and second portions operable to store damping fluid. The apparatus further comprises a first sensor for generating a first electrical signal in response to the difference in pressure between the damping fluid in the first and second portions of the working chamber. A second sensor is also provided which is able to generate a second electrical signal in response to the movement of the body of the automobile. A computer is used for generating an electrical control signal in response to the first and second electrical signals. Finally, the apparatus further comprises a solenoid for regulating the flow of damping fluid between the first and second portions of the working chamber in response to the output of the computer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to automotive suspension systems, and moreparticularly to a method and apparatus for absorbing mechanical shock.

2. Description of Related Art

Shock absorbers are used in conjunction with automotive suspensionsystems to absorb unwanted vibration which occur during driving. Toabsorb this unwanted vibration, shock absorbers are generally connectedbetween the body and the suspension of the automobile. A piston islocated within the shock absorber and is connected to the body of theautomobile through a piston rod. Because the piston is able to limit theflow of damping fluid within the working chamber of the shock absorberwhen the shock absorber is compressed, the shock absorber is able toproduce a damping force which counteracts the vibration which wouldotherwise be transmitted from the suspension to the body. The greaterthe degree to which the flow of damping fluid within the working chamberis restricted by the piston, the greater the damping forces which aregenerated by the shock absorber.

In selecting the amount of damping that a shock absorber is to provide,three vehicle performance characteristics are often considered: ridecomfort, vehicle handling and road holding ability. Ride comfort isoften a function of the spring constant of the main springs of thevehicle, as well as the spring constant of the seat, tires, and theshock absorber. Vehicle handling is related to the variation in thevehicle's attitude (i.e., roll, pitch and yaw). For optimum vehiclehandling, relatively large damping forces are required to avoidexcessively rapid variation in the vehicle's attitude during cornering,acceleration, and deceleration. Road holding ability is generally afunction of the amount of contact between the tires and the ground. Tooptimize road holding ability, large damping forces are required whendriving on irregular surfaces to prevent loss of contact between thewheels and the ground for an excessive period of time.

To optimize ride comfort, vehicle handling, and road holding ability, itis generally desirable to have the damping forces generated by the shockabsorber be responsive to the input frequency from the road. When theinput frequency from the road is approximately equal to the naturalfrequency of the body of the automobile (e.g., approximately between 0-2Hz), it is generally desirable to have the shock absorber provide largedamping forces to avoid excessively rapid variation the vehicle'sattitude during cornering, acceleration and deceleration. When the inputfrequency from the road is between 2-10 Hz, it is generally desirable tohave the shock absorber provide low damping forces so as to produce asmooth ride and allow the wheels to follow changes in road elevation.When the input frequency from the road is approximately equal to thenatural frequency of the automobile suspension (i.e., approximately10-15 Hz), it may be desirable to have relatively low damping forces toprovide a smooth ride, while providing sufficiently high damping forcesso as to prevent excessive loss of contact between the wheels and theground.

One method for selectively changing the damping characteristics of ashock absorber is between the wheels and the ground.

One method for selectively changing the damping characteristics of ashock absorber is disclosed in U.S. Pat. No. 4,597,411. In thisreference, a solenoid is used to selectively open and close an auxiliaryopening in a base valve of a shock absorber. The base valve thenregulates the pressure inside one portion of the working chamber of theshock absorber so as to control damping. Another method for selectivelychanging the damping characteristics of a shock absorber is disclosed inPCT application PCT/SE85/00212 published Jan. 9, 1987. In oneembodiment, this reference discloses the use of a pressure sensor tocount the number of compression-rebound cycles of the absorber, as wellas an accelerometer attached to the wheel support to determine thevertical velocity of the body of the automobile. The dampingcharacteristics of the absorber are then changed in response to thevertical velocity of the body.

A further method for selectively changing damping characteristics ofshock absorbers is disclosed in United Kingdom Patent Application GB 2147 683 A. In one embodiment, this reference discloses a valve diskwhich is used to cover channels in a valve body which transfers dampingfluid between the upper and lower portions of the working chamber. Thevalve disk is biased against the valve body by a support member which isdisposed partially within a pressure chamber. The pressure chambercommunicates with the lower portion of the working chamber through afirst flow path, and to the upper portion of the working chamber througha second flow path. To regulate the flow of damping fluid through thesecond flow path and hence the pressure in the pressure chamber actingon the support member, an auxiliary valve plate is provided. Theauxiliary valve plate is disposed over the second flow path andcooperates with a coil which is located on the valve body below aportion of the auxiliary valve plate. When the coil is energized, themagnetic flux generated by the coil produces a biasing force on theauxiliary valve disk causing the auxiliary valve disk to deflect,thereby increasing the opening between the second flow path and theupper portion of the working chamber. Accordingly, when the coil biasesthe auxiliary valve disk in the position to allow more hydraulic fluidto flow through the second flow path, the pressure of the damping fluidin the pressure chamber declines thereby reducing the force transmittedto the valve plate by the support member. The pressure in the lowerportion of the working chamber causes the valve plate to deflect,thereby increasing the amount of damping fluid flowing through thechannels.

SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to providea method and apparatus for absorbing mechanical shock which is able topermit simultaneous damping of the movement of the body of an automobileas well as the movement of the wheels and axles of the vehicle.

Another object of the present invention is to provide a method andapparatus for absorbing mechanical shock which are able to counteracttendencies of an automobile to roll, pitch or yaw during turning,acceleration, or braking.

It is a further object of the present invention is to provide a methodand apparatus for absorbing mechanical shock which are able to providean acceptable level of friction between the road surface and the tire ofan automobile so as to maintain the braking and deceleration capabilityof the automobile.

Another object of the present invention is to provide a method andapparatus for absorbing mechanical shock which are able to generate anadjustable damping characteristic for the body of an automobile inresponse to different driving environments and different driving habits.

A further object of the present invention is to provide a new andimproved direct acting hydraulic shock absorber having a high degree offlexibility with respect to installation on different models ofautomobiles. In this regard, a related object of the present inventionis to provide an apparatus for absorbing mechanical shock which arerelatively low in cost and relatively easy to maintain.

It is a more particular object of the present invention to provide a newand improved shock absorber of the above character which utilizes asolenoid to control the flow of damping fluid through various passagesin the apparatus under various operating conditions so as to control thedamping forces provided by the apparatus.

Yet another object of the present invention is to provide a shockabsorber, as described above, in which the damping forces are controlledby a computer which is responsive to the pressure differential betweentwo portions of the working chamber of the apparatus.

It is another object of the present invention to provide a method andapparatus for absorbing mechanical shock in which the damping forces arecontrolled by a computer which is responsive to the vertical movement ofthe body of the vehicle.

An additional object of the present invention is to provide a method andapparatus for absorbing mechanical shock in which the damping forces arecontrolled by a computer which can be reprogrammed so that the apparatuscan provide a different damping characteristic.

BRIEF DESCRIPTION OF THE DRAWINGS

Various advantages of the present invention will become apparent to oneskilled in the art upon reading the following specification and byreference to the following drawings in which:

FIG. 1 is the schematic representation of the apparatus for absorbingmechanical shock according to the teachings of the preferred embodimentof the present invention as shown in operative association with thetypical automobile;

FIG. 2 is a reduced side elevational view, partially broken away, of theapparatus for absorbing mechanical shock shown in FIG. 1 according tothe first preferred embodiment of the present invention;

FIGS. 3 and 4 is an enlarged elevated prospective exploded view of thepiston according to the first preferred embodiment of the apparatus forabsorbing mechanical shock as shown in FIG. 2;

FIG. 5 is an enlarged longitudinal cross-sectional view showing thepiston according to the first preferred embodiment of the presentinvention as shown in FIG. 2;

FIGS. 6-9 are enlarged cross-sectional views of the piston shown in FIG.5 illustrating the operation of the piston according to the firstpreferred embodiment of the present invention;

FIG. 10 is an illustration of the manner in which the outputs from thepressure sensor and accelerometer are used to operate the solenoid ofthe first preferred embodiment of the present invention as shown in FIG.5;

FIG. 11 is a schematic diagram of the driving circuit illustrated inFIG. 10;

FIG. 12 is a flow chart illustrating a method for damping the movementof the body of an automobile which may be used in conjunction with theapparatus for damping mechanical shock according to the first and secondpreferred embodiments of the present invention;

FIG. 13 is a flow chart illustrating a method for minimizing thevibration of the wheel or unsprung mass of an automobile which may beused in conjunction with the apparatus for absorbing mechanical shockaccording to the first and second preferred embodiments of the presentinvention;

FIG. 14 is a flow chart illustrating a method for preventing excessiveaxial movement of the piston during compression and rebound which may beused in conjunction with the apparatus for absorbing mechanical shockaccording to the first and second preferred embodiments of the presentinvention; and

FIG. 15 is an enlarged longitudinal cross-sectional view of theapparatus for absorbing mechanical shock shown in FIG. 1 according tothe second preferred embodiment of the present invention.

FIG. 16 is an enlarged longitudinal cross-sectional view of theapparatus for absorbing mechanical shock shown in FIG. 1 according tothe third preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a plurality of four shock absorbers 20 inaccordance with the preferred embodiments of the present invention areshown. The shock absorbers 20 are depicted in operative association witha diagrammatic representation of a conventional automobile 22. Theautomobile 22 includes a rear suspension 24 having a transverselyextending rear axle assembly 26 adapted to operably support thevehicle's rear wheels 28. The axle assembly 26 is operably connected tothe automobile 22 by means of a pair of shock absorbers 20 as well as bythe helical coil springs 30. Similarly, the automobile 22 has a frontsuspension system 32 including a transversely extending front axleassembly 34 to operatively support the front wheels 36. The front axleassembly 34 is operatively connected to the automobile 22 by means of asecond pair of the shock absorbers 20 and by the helical coil springs38. The shock absorbers 20 serve to damp the relative movement of theunsprung portion (i.e., the front and rear suspensions 32 and 24) andthe sprung portion (i.e., the body 39) of the automobile 22. While theautomobile 22 has been depicted as a passenger car, the shock absorber20 may be used with other types of automotive vehicles as well.

With particular reference to FIG. 2, the shock absorber 20 according tothe preferred embodiments of the present invention is shown. The shockabsorber 20 comprises an elongated tubular pressure cylinder 40 defininga damping fluid containing working chamber 42. Disposed within theworking chamber 42 is a reciprocable piston 44 that is secured to oneend of an axially extending piston rod 46. The piston 44 includes acircumferential groove 48 operable to retain a piston ring 50 as is wellknown in the art. The piston ring 50 is used to prevent damping fluidfrom flowing between the outer periphery of the piston 44 and the innerdiameter of the cylinder 40 during movement of the piston 44. A basevalve, generally designated by the numeral 52, is located within thelower end of the pressure cylinder 40 and is used to control the flow ofdamping fluid between the working chamber 42 and an annular fluidreservoir 54. The annular fluid reservoir 54 is defined as the spacebetween the outer periphery of the cylinder 40 and the inner peripheryof a reservoir tube or cylinder 56 which is arranged centrally aroundthe exterior of the pressure cylinder 40. The construction and operationof the base valve 52 may be of the type shown and described in U.S. Pat.No. 3,771,626, which is hereby incorporated by reference.

The upper and lower ends of the shock absorber 20 are provided withgenerally cup-shape upper and lower end caps 58 and 60 respectively. Theend caps 58 and 60 are secured to opposing ends of the reservoir tube 56by a suitable means such as welding. The shock absorber 20 is shown asbeing provided with a dirt shield 62 which is secured at its upper endto the upper end of the piston rod 46. Suitable end fittings 64 aresecured to the upper end of the piston rod 46 and the lower end cap 60for operatively securing the shock absorber 20 between the body and theaxle assembly of the automobile 22. Those skilled in the art willappreciate that, upon reciprocal movement of the piston 44, dampingfluid within the pressure cylinder 40 is transferred between the upperand lower portions of the working chamber 42, and between the workingchamber 42 and the fluid reservoir 54. By controlling the flow ofdamping fluid between the upper and lower portion of the working chamber42, the shock absorber 20 is able to controllably dampen relativemovement between the body and the suspension of the automobile 22 so asto optimize both ride comfort and road handling ability. Toward thisend, the piston 44 is provided with a new and improved valvingarrangement for selectively controlling the flow of damping fluidbetween the upper and lower portions of the working chamber 42 duringreciprocal movement thereof, as will hereinafter be described in detail.

According to the first preferred embodiment of the present invention,the piston 44 comprises a valve body 66 having a first and secondplurality of vertical flow passages 68 and 70. The flow passages 68 and70 extend between the upper surface 72 of the valve body 66 and thelower surface 74 of the valve body 66. Each of the flow passages 68comprises a valve controlled upper outlet end portion 76 and a lowercounter-recessed inlet end portion 78. Similarly, each of the flowpassages 70 comprises a valve controlled lower outlet end portion 80 andan upper counter-recessed inlet end portion 82.

To provide means for controlling the flow of damping between the upperand lower portions of the working chamber 42, two valve disks 84 and 86are provided. The valve disks 84 and 86 are coaxially arranged adjacentto the upper surface 72 and the lower surface 74 of the valve body 66respectively. The valve disk 84 is of a sufficient diameter so as toregister with and cover the outlet end portions 76 of the flow passages68 thereby preventing damping fluid from entering the outlet endportions 76. However, the valve disk 84 does not cover thecounter-recessed inlet end portions 82 of the flow passages 70 so as toallow damping fluid to enter the counter-recessed inlet end portions 82.The valve disk 84 also cooperates with a recessed portion 88 on theupper surface 72 of the valve body 66 so as to form a first pressurechamber 90. Correlatively, the valve disk 86 is of a diameter so as toregister with and cover the outlet end portions 80 of the flow passages70 while not covering the counter-recessed inlet end portions 78. Inaddition, the valve disk 86 cooperates with a second recessed portion 92on the lower surface 74 on the valve body 66 to form a second pressurechamber 94.

To support the valve body 66 within the pressure cylinder 40, the valvebody 66 has a central bore 96 operable to receive an axially extendingpiston post 98. The piston post 98 has an upper portion 100 with aninternally threaded central bore 102 adapted to threadably engage anexternally threaded lower end portion 104 of the piston rod 46. Tworadially extending flow passages 105 are disposed on the piston post 98which communicate with two flow passages 106 which radially extend fromthe pressure chamber 94 to the central bore 96 of the valve body 66. Theflow passages 105 and 106 allow damping fluid to flow between thepressure chamber 94 and the solenoid described below. The piston post 98further includes a radially extending step 107 having an outsidediameter greater than the diameter of the central bore 96. Because thestep 107 is disposed above the valve body 66, the step 107 limits upwardmovement of the valve body 66 relative to the piston post 98. Inaddition, a piston retaining nut 108 is provided having an internallythreaded bore 109 which threadably engages an externally threaded lowerportion 110 of the piston post 98 at a position below the valve body 66.Because the outside diameter of the piston retaining nut 108 is greaterthan the diameter of the central bore 96 of the valve body 66, the nut108 prevents downward movement of the valve body 66 relative to thepiston post 98. The piston post 98 and the piston retaining nut 108 alsoserve to secure the innermost portions of the valve disks 84 and 86. Inthis regard, the innermost portion of the valve disk 84 engages both theradially extending step 107 of the piston post 98 and the upper surface72 of the valve body 66. In addition, the radially innermost portion ofthe valve disk 86 engages the lower surface 74 of the valve body 66 andthe piston retaining nut 108.

To bias the valve disks 84 and 86 against the surfaces 72 and 74 of thevalve body 66, a pair of coaxially arranged, axially spaced, helicalcoil springs 112 and 114 are provided. The spring 112 is disposedcoaxially with the piston post 98 between a radially extending step 116formed on the piston post 98 and an intermediate backing plate 118 whichis located coaxially with, and adjacent to, the upper surface of thevalve disk 84. By means of the intermediate backing plate 118, thespring 112 is able to resiliently and yieldably bias the valve disk 84against the upper surface 72 of the valve body 66. Similarly, the spring114 is disposed between a radially extending flange 120 on the pistonretaining nut 108 and an intermediate backing plate 122 which is locatedadjacent to, and coaxially with, the valve disk 86. The spring 114 istherefore able to resiliently and yieldably biases the valve disk 86against the lower surface 74 of the valve body 66 via the intermediatebacking plate 122.

In accordance with the principles of the present invention, the piston44 further comprises a solenoid 124 so as to provide an electricalcontrollable flow means operable to control the actuation of the valvedisks 84 and 86. The solenoid 124 includes a housing 126 which isdisposed coaxially within the central bore 128 of the piston post 98.Within the housing 126 are disposed a coil 130 and an armature 132having an enlarged counterbore 134. The armature 132 is biased axiallyupwardly relative to the valve body 66 by a helical coil spring 136which is disposed within the counterbore 134. The upper end of thespring 136 bears against a radial surface 138 in the counterbore 134,whereas the lower end of the spring 136 bears against the upper side ofa sealing plate 140. An O-ring or similar type sealing element 142 isdisposed between the coil 130 and the armature 132 to prevent dampingfluid to flow therebetween. An annular ring 144 is provided between thecoil 130 and the sealing plate 140 to ensure that the spatial separationbetween the coil 130 and the sealing plate 140 remains constant.

The solenoid 124 also comprises an annular ring 146 of ferro-magneticmaterial disposed adjacent to the coil 130 between the armature 132 andthe housing 126. The annular ring 146 is used to complete the magneticflux path generated by the coil 130 to ensure proper operation of thesolenoid 124. In addition, the solenoid 124 also comprises an annularhousing cap 148 disposed horizontally within the upper portion 150 ofthe housing 126. The housing cap 148 has a centrally disposed axial flowpassage 152 which allows damping fluid inside the housing 126 to flow toone surface of a pressure sensor described below. To secure the solenoid124 within the piston post 98, an externally threaded solenoid retainingplug 153 is provided. The solenoid retaining plug 153 engages aninternally threaded portion lower portion 110 of the piston post 98. Theplug 153 comprises an axially extending central bore 154 which allowsdamping fluid to flow between the sealing plate 140 and the lowerportion of the working chamber 42.

The solenoid 124 operatively cooperates with the sealing plate 140 tocontrol the flow of damping fluid between a central flow passage 155 anda plurality of radially displaced flow passages 156 which are disposedon the sealing plate 140. When the solenoid 124 is not energized,damping fluid is able to flow between the central flow passage 155 andthe radially displaced flow passages 156. When the solenoid 124 isenergized, the armature 132 moves downwardly against the force of thespring 136 to a position in sealing engagement with the sealing plate140. When this occurs, the armature 132 prevents the flow of fluidbetween the passages 155 and 156. An O-ring or similar sealing element158 is provided on the armature 132 which prevents the flow of dampingfluid between the armature 132 and the sealing plate 140 when thesolenoid 124 is energized.

To allow the fluid flowing through the passages 155 and 156 tocounter-bias the valve disks 84 and 86, the valve body 66 furthercomprises the flow passages 160 and 162. The flow passage 160 extendsaxially from the pressure chamber 90 to the pressure chamber 94, whilethe flow passage 162 radially extends from the flow passage 70 to thepressure chamber 94. Because damping fluid in the pressure chamber 94 isable to flow to the radially displaced flow passages 156 on the sealingplate 140 by means of the flow passage 106 in the valve body 66 and theflow passage 105 in the piston post 98, two flow paths are formed withinthe valve body 66. The first flow path permits damping fluid to flowfrom the upper portion of the working chamber 42 to the lower portion ofthe working chamber 42. In this regard, the first flow path allowsdamping fluid in the upper portion of the working chamber 42 to flowfrom the vertical flow passage 70 to the pressure chamber 94 through theflow passage 162. Damping fluid in the pressure chamber 94 is thereforeable to flow to the radially displaced flow passages 156 on the sealingplate 140 through the flow passage 105 in the piston post 98 and theflow passage 106 in the valve body 66. If the solenoid 124 is notenergized, damping fluid flowing through the radially displaced passages156 is able to flow into the lower portion of the working chamber 42through the central flow passage 155 of the sealing plate 140 and thecentral bore 154 of a solenoid retaining plug 153.

The second flow path permits damping fluid to flow between the lowerportion of the working chamber 42 and the pressure chamber 90. In thisregard, the second flow path allows damping fluid in the lower portionof the working chamber 42 to flow through the central bore 154 ofsolenoid retaining plug 153 to the central flow passage 155 in thesealing plate 140. If the solenoid 124 is not energized, damping fluidflowing through the central bore 154 is able to flow into the pressurechamber 94 through the radially displaced flow passages 156 on thesealing plate 140, the flow passage 105 in the piston post 98 and theflow passage 106 in the valve body 66. Damping fluid is than able toflow from the pressure chamber 94 to the pressure chamber 90 through theflow passage 160.

To prevent leakage of damping fluid in the pressure chamber 90, anannular retaining seal 164 is provided. The annular retaining seal 164is disposed within the pressure chamber 90 adjacent to the valve disk 84so as to prevent damping fluid inside the pressure chamber 90 fromentering the upper portion of the working chamber 42. An annularretaining ring 168 is also disposed within the pressure chamber 90adjacent to the annular retaining seal 164 to ensure that the seal 164is not displaced in such a manner as to allow hydraulic leakage betweenthe pressure chamber 90 and the upper portion of the working chamber 42.In a similar fashion, an annular retaining seal 170 is disposed withinthe chamber 94 adjacent to the valve disk 86. The annular retaining seal170 is used to prevent damping fluid inside the pressure chamber 94 fromentering the lower portion of the working chamber 42. An annularretaining ring 172 is also disposed within the pressure chamber 94adjacent to the annular retaining seal 164 to ensure that the seal 170is not displaced in such a manner as to permit leakage of damping fluidbetween the pressure chamber 94 and the lower portion of the workingchamber 42.

In operation of the shock absorber 20 according to the present inventionas shown in FIGS. 6-9, the position of the armature 132 is dependentupon whether the shock absorber 20 is in compression or rebound, andwhether a firm or soft stroke is desired. When a soft compression strokeis desired, the solenoid 124 remains idle as shown in FIG. 6, therebyallowing damping fluid in the lower portion of the working chamber 42 toflow through the central bore 154 of the solenoid retaining plug 153 andthe flow passages 155 and 156 of the sealing plate 140 to the flowpassage 105 in the piston post 98. Damping fluid is than able to flowfrom the flow passage 105 in the piston post 98 to the pressure chamber90 through the flow passage 106 in the valve body 66, the pressurechamber 94, and the flow passage 160. Because the flow of damping fluidto the pressure chamber 90 causes the pressure inside the pressurechamber 90 to exceed the pressure in the upper portion of the workingchamber 42, a pressure differential is created across the valve disk 84.This pressure differential counter-biases the valve disk 84 so as toallow more damping fluid to flow through the flow passage 68 than wouldotherwise be permitted. By allowing more damping fluid to flow throughthe flow passage 68, a soft compression stroke is produced. When a firmcompression stroke is desired, the solenoid 124 is actuated as shown inFIG. 8, thereby preventing damping fluid from flowing from the centralpassage 155 to the radially displaced passages 156 of the sealing plate140. Because damping fluid in the lower portion of the working chamber42 is thereby prevented from entering the pressure chamber 90, thepressure inside the pressure chamber 90 is substantially the same as thepressure inside the upper portion of the working chamber 42. Since nopressure differential is created across the valve disk 84 due to thedamping fluid inside the pressure chamber 90, no counter-biasing forceacts on the valve disk 84 other than that produced by the damping fluidflowing through the flow passage 68. Accordingly, the valve disk 84allows less fluid to flow through the flow passage 68 so as to produce afirm compression stroke.

When a firm rebound stroke is desired, the solenoid 124 is not energizedas shown in FIG. 7 so that the spring 136 biases the armature 132 in itsraised position. Damping fluid from the upper portion of the workingchamber 42 which flows into the pressure chamber 94 through the flowpassages 70 and 162 in the valve body 66 is therefore able to flow tothe radially displaced flow passages 156 in the sealing plate 140through the flow passage 105 in the piston post 98 and the flow passage106 in the valve body 66. Because the armature 132 is biased upward,damping fluid flowing to the radially displaced passages 156 is able toflow to the lower portion of the working chamber 42 through the centralflow passage 155 in the sealing plate 140 and the central bore 154 ofthe solenoid retaining plug 153. Because the pressure inside thepressure chamber 94 is therefore substantially the same as the pressurein the lower portion of the working chamber 42, no pressure differentialis created across the valve disk 86 due to the damping fluid in thepressure chamber 94. Accordingly, the only counter-biasing force whichacts on the valve disk 86 is that provided by the damping fluid flowingthrough the flow passage 70. Because the counter-biasing force acting onthe valve disk 86 is less than would otherwise be provided if thesolenoid 124 was energized, fluid flowing through the passage 70 isreduced thereby producing a firm rebound stroke. When a soft reboundstroke is desired, the solenoid 124 is energized as shown in FIG. 9,thereby preventing the flow of damping fluid between the central flowpassages 155 and the radially displaced flow passages 156. Accordingly,damping fluid entering the pressure chamber 94 from the upper portion ofthe working chamber 42 through the flow passages 70 and 162 remains inthe pressure chamber 94. The pressure inside the pressure chamber 94therefore becomes greater than the pressure inside the lower portion ofthe working chamber 42. Because a pressure differential is createdacross the valve disk 86, the resulting counter-biasing force acting onthe valve disk 86 allows a greater amount of damping fluid to flowthrough the passage 70 thereby producing a soft rebound stroke.

In accordance with the principles of the present invention, the shockabsorber 20 further comprises a pressure sensor 180 to provide means fordetermining the difference in pressure between the damping fluid in theupper and lower portions of the working chamber 42. The pressure sensor180 is mounted on an annular member 182 which is disposed within thepiston post 98 between the piston rod 46 and a radially inward extendingstep portion 184 formed within the central bore 128 of the piston post98. The annular member 182 has a radially extended passage 186 and anaxial passage 188 which extends partially through the annular member182. The radially extended passage 186 communicates with the axialpassage 188 at the radially inner end of the radially extended passage186. The radially extended passage 186 also communicates at its radiallyouter end with a flow passage 190 formed on the piston post 98. Becausethe pressure sensor 180 is mounted over the axial passage 188, dampingfluid from the upper portion of the working chamber 42 is able to flowto a first surface 192 of the pressure sensor 180 through the passages190 and 186. In addition, damping fluid in the lower portion of theworking chamber 42 is able to flow through the central bore 154 of thesolenoid retaining plug 153, the central flow passage 155 in the sealingplate 140, the counterbore 134 of the armature 132, and the flow passage152 in the housing cap 148 to a second surface 194 of the pressuresensor 180. By virtue of the foregoing structure, the first and secondsurfaces 192 and 194 of the pressure sensor 180 are in fluidcommunication with the damping fluid in the first and second portions ofthe working chamber 42. The pressure sensor 180 is therefore able togenerate a signal representing the differential pressure between thedamping fluid in the upper and lower portions of the working chamber 42.

To provide means for determining the movement of the body of theautomobile 22, an accelerometer 196 is provided which is disposed on theannular member 182. Because the accelerometer 196 is secured to theannular member 182, the accelerometer 196 is able to move in unison withthe piston rod 46, and therefore with the body of the automobile 22.Accordingly, the accelerometer 196 is able to generate an electricalsignal responsive to the vertical acceleration of the body of theautomobile 22. By performing numerical integration on the output fromthe accelerometer 196, the vertical velocity of the body of theautomobile 22 may also be determined.

To provide means for generating an electrical control signal forenergizing the solenoid 124 in response to the outputs from the pressuresensor 180 and the accelerometer 196, the shock absorber 20 furthercomprises a signal conditioning circuit generally designated by thenumeral 198 which is disposed within the piston post 98. A firstplurality of conductors 200 extend through the annular member 182 toallow electrical communication between the conditioning circuit 198 andthe pressure sensor 180 and the accelerometer 196. As shown in FIG. 10,the signal conditioning circuit 198 amplifies the output from thepressure sensor 180 and the accelerometer 196 prior to a delivery to acomputer generally designated by the numeral 202. The computer 202 isused to generate an A output and a B output in response to theelectrical signals from the output of the signal conditioning circuit198 according to one of several stored programs described below. Thecomputer 202 generates a logically high or low A output when thecompression stroke is to be soft or firm respectively. Similarly, thecomputer 202 generates electrically high or electrically low B outputwhen the rebound strike is to be soft or firm respectively. The A and Boutputs from the computer 202 are then delivered to the solenoid 124through a solenoid driving circuit generally designated as 204. Thesolenoid driving circuit 204 is used for converting the output from thecomputer 202 as well as the output from the signal conditioning circuit198 into voltage levels which may be used to actuate the solenoid 124. Asecond plurality of conductors 206 is used for delivering the outputfrom the computer 202 and the signal conditioning circuit 198 throughthe annular member 182 to the solenoid driving circuit 204.

As shown in FIG. 11, the driving circuit 204 comprises a comparator 208which receives an output signal from the signal conditioning circuit 198as well as from an adjustable voltage supply which is represented by thevariable resistor 210. The output from the signal conditioning circuit198 which is delivered to the driving circuit 204 is a voltageresponsive to the pressure differential between the upper portion andlower portion of the working chamber 42. When the pressure in the lowerportion of the working chamber 42 exceeds the pressure in the upperportion by a predetermined level (i.e., during rebound), a voltage isgenerated at the output of the signal conditioning circuit 198 whichexceeds the voltage delivered by the variable resistor 210. When thisoccurs, a logical high output is produced at the output of thecomparator 208. If the pressure in the lower portion of the workingchamber 42 is less than the pressure in the upper portion of the workingchamber 42, the voltage delivered by this signal conditioning circuit198 to the comparator 208 is less than the voltage delivered by thevariable resistor 210. When this occurs, a logical low voltage at theoutput of the comparator 208.

To ensure that the voltage delivered to the various logic gatesdescribed below is of a compatible magnitude, the output of thecomparator 208 is delivered through a resistor 212 to an inverter 214,and to ground through a resistor 216. The resistors 212 and 216 serve toensure that the voltage delivered to the inverter 214 is within a rangethat will enable the inverter 214 to produce a responsive output whichis compatible with the other components of the driving circuit 204described below. The output of the comparator 208 is also connected tothe capacitor 218 which serves to filter the relatively high frequencynoise present at the output of the comparator 208. The output from theinverter 214 is connected to a NOR gate 220 and an AND gate 222. The NORgate 220 and the AND gate 222 also receive the A output and the B outputof the computer 202. In addition, the A output and the B output are alsodelivered to an XOR gate 224, and the A output and the output from theXOR gate 224 are delivered to the AND gate 226. Because the output fromthe gates 220, 222 and 226 are connected to an OR gate 228, the outputfrom the OR gate 228 responds according to the following table:

    ______________________________________                                        Output from                                                                   Computer 202    Output from                                                   A             B     OR Gate 228                                               ______________________________________                                        0             0     P                                                         0             1     1 (On)                                                    1             0     0 (Off)                                                   1             1     P                                                         ______________________________________                                    

where:

P indicates that the solenoid 124 is to be energized when the outputfrom the pressure sensor 180 is positive (i.e., when the piston 44 is inrebound)

P indicates that the solenoid 124 is to be energized when the outputfrom the pressure sensor 180 is not positive (i.e., when the piston 44is in compression)

1 indicates that the solenoid 124 is to be energized during bothcompression and rebound;

0 indicates that the solenoid is to remain unenergized during bothcompression and rebound.

Accordingly, when the A output and the B output from the computer 202are both low, the solenoid driving circuit 204 directs the solenoid 124to respond directly to the output from the pressure sensor 180.Similarly, if both the A output and the B output are both high, thedriving circuit 204 directs the solenoid 124 to follow the invertedoutput from the pressure sensor 180. If only the B output is high, thedriving circuit 204 causes the solenoid 124 to energize, while thesolenoid 124 remains unenergized when only the A output is high.

The output from the OR gate 228 is delivered to the IN pin 1 of a drivecontroller 230. The drive controller 230 is used for controlling thebase current delivered to an external power NPN Darlington transistor234 that drives the solenoid 124. The drive controller 230 initiallypermits the transistor 234 to provide a sufficiently large current tocause the armature 132 to engage the sealing plate 140. After thearmature 132 engages the sealing plate 140, the drive controller 230reduces the current delivered to the solenoid 124 to a level whichmaintains the position of the armature 132 relative to the sealing plate140. To drive the controller 230, the SUPPLY pin 7 of the controller 230is connected to the supply bus V_(cc) which carries a nominal potentialof 5 volts. The TIMER pin 8 of the controller 230 is also connected tothe V_(cc) supply bus through a resistor 236, and to ground through thecapacitor 238. The values of the resistor 236 and the capacitor 238determine the time after which the solenoid 124 is initially actuatedthat the current through the solenoid 124 is reduced.

The OUTPUT pin 2 of the controller 230 is connected to the base of thetransistor 234, as well as to one plate of the capacitor 240. The secondplate of the capacitor 240 is connected to the COMP pin 3 of thecontroller 230 so that the capacitor 240 is able to provide stabilityfor the circuit when the solenoid 124 is being held in its actuatedstate. The SENSE INPUT pin 4 of the controller 230 is connected to theemitter of the transistor 234 through a resistor 242, and to groundthrough a resistor 244. The resistors 242 and 244 serve to establish theminimum current required to hold the solenoid 124 in its actuated state.A diode 246 is also connected between the emitter of the transistor 234and ground to ensure that the voltage at the emitter of the transistor234 is equal to forward bias voltage of the diode 246 (approximately 0.7volts). To protect the transistor 234 from inductive kickback when thecurrent to the solenoid 124 is reduced, a zener diode 248 is provided.The zener diode 248 provides a path for current from the solenoid 124when the voltage across the diode 248 exceeds the breakdown potential ofthe diode 248 (approximately 35 volts). The diode 248 thereby limits thevoltage delivered to the collector of the transistor 234 to 35 volts soas to reduce the impact of inductive kickback on the transistor 234.

The information which is delivered by the accelerometer 196 and thepressure sensor 180 may be used to damp the movement of the vehicle bodyin the manner shown in FIG. 12. Initially, the compression stroke andthe rebound stroke are soft as shown in step 250, indicating that thesolenoid 124 remains unactuated during the compression stroke but isactuated during the rebound stroke. At step 252, the output from theaccelerometer 196 is read by the computer 202, and is added to the prioracceleration readings at step 254 so as to obtain the vertical velocityV_(body) of the body of the automobile 22. At step 256, the computer 202determines whether the magnitude of the velocity obtained from theaccelerometer 196 is greater than a predetermined value V_(o) which maytypically have a value of 0.05 m/s. If the vertical velocity V_(body) isless than the predetermined value V_(o), the solenoid 124 remains in itsunactuated state during compression and in its actuated state duringrebound as shown in step 258. If the magnitude of the vertical velocityof the body of the automobile 22 is greater than the predetermined valueV_(o), the computer 202 then determines at step 260 whether the body ofthe automobile 22 is moving upward or downward with respect to the road.As shown in step 262, if the vertical velocity V_(body) is positiveindicating an upward movement, the solenoid 124 remains unactuatedduring both the compression and rebound strokes to produce a firmrebound stroke and a soft compression stroke. If the vertical velocityV_(body) is negative, the computer 202 actuates the solenoid 124 duringboth compression and rebound as shown in step 264. After the response ofthe solenoid 124 is determined according to the steps 250-264, theprocessing returns to the step 250 via step 266 or another initial stepin another method. By using this method, the shock absorber 20 is ableto provide maximum damping when the frequency of the vertical movementof the body of the automobile 22 is substantially equal to 1.5 Hz.

To minimize the vibration of the body of the automobile 22 due to anatural frequency of the wheels 28 and 36, the computer 202 may be usedto control the solenoid 124 in the manner shown in FIG. 13. The pressuredifferential between the upper and lower portions of the working chamber42 is initially read at step 268. At step 270, successive pressuremeasurements are taken during a time interval which is approximatelyequal to the natural frequency of the wheels (typically 10-15 Hz). Thevalues of the pressure differential are then used to determine the valueof A² at step 272 according to the following equation at step 272:##EQU1## where:

P_(t) is the differential pressure between the upper portion and thelower portion of the working chamber 42 at time t; and

T is the period of the selected natural frequency of the wheels of theautomobile 22 (typically 10-15 Hz).

At step 274, the value of A² is compared with the value of A_(o) ² whichrepresents a preselected constant chosen to allow the shock absorber togo to firm when the velocity of the piston exceeds 0.4 m/s. It is to beunderstood, however, that A_(o) ² may be chosen to optimize a particularride characteristic. If the value of A² is greater than the value ofA_(o) ², the solenoid 124 is actuated during compression so as toproduce a firm compression stroke, while remaining unactuated duringrebound so as to produce a firm rebound stroke as shown in step 276. Ifthe value of A² is less than or equal to A_(o) ², then the actuation ofthe solenoid 124 remains unchanged from its prior state. Processing thenreturns to step 268 via step 278 or the initial step of another method.By using this method, the shock absorber 20 is able to provide maximumdamping when the frequency of the vertical movement of the wheels of theautomobile 22 is substantially equal to a value between 10-15 Hz.

To prevent the piston 44 and the piston rod 46 from excessive axialmovement during compression and rebound, the method illustrated in FIG.14 may be used. At step 280, the pressure differential between the upperand lower portions of the working chamber 42 is recorded. By determiningthe value of the differential pressure at step 282, the computer 202determines whether the shock absorber 20 is in compression or rebound.As shown in step 284, if the shock absorber 20 is in compression and thesolenoid 124 has been actuated so as to produce a firm compressionstroke, the processing returns to step 280 via step 286 or to theinitial step of another method. If the compression stroke is soft, thepiston velocity V_(piston) is determined at step 288 by comparing thepressure differential recorded by the pressure sensor 180 with apressure/piston velocity table which is stored in the memory of thecomputer 202. If the absolute value of the piston velocity V_(piston) isgreater than a predetermined value V_(o) (typically 0.4 m/s) as shown bystep 290, the solenoid 124 is deactivated thereby producing a firmcompression stroke at step 292. Processing then returns to step 280 viastep 286 or to the initial step of another method. If the absolute valueof the piston velocity V_(piston) is less than the predetermined valueV_(o), processing also returns to step 280 via the step 286 or theinitial step of another method.

If the shock absorber 20 is in rebound as determined at step 282, thecomputer 202 determines whether the solenoid 124 is producing a firm orsoft rebound stroke as illustrated at step 294. If the rebound stroke isfirm, the processing returns to the step 280 via the step 286 or aninitial step in another method. If the rebound stroke is soft, thepiston velocity V_(piston) is determined at step 296 by comparing thepressure differential between the upper and the lower portions of theworking chamber 42 to a pressure/piston velocity table which is storedin the memory of the computer 202. As shown at step 298, if themagnitude of the piston velocity V_(piston) is greater than apredetermined value V_(o), the computer 202 deactivates the solenoid 124at step 300 to produce a firm rebound stroke. If the magnitude of thepiston velocity V_(piston) is less than the predetermined value V_(o),the processing returns to step 280 via the step 286 or an initial stepin another method. By using this method, the shock absorber 20 is ableto provide maximum damping when the vertical movement of the wheels ofthe automobile 22 would otherwise result in over compression or overextension of the shock absorber 20.

A second preferred embodiment of the present invention is shown in FIG.15. In this embodiment, the valve body 302 comprises an upper surface304 with a recess portion 306, and a lower surface 308 with a recessportion 310. To allow fluid communication between upper and lowerportions of the working chamber 42, the valve body 302 further comprisesa first and second plurality of vertical flow passages 312 and 314. Theflow passages 312 and 314 extend between the upper surface 304 of thevalve body 302 and the lower surface 308 of the valve body 302. Each ofthe flow passages 312 comprises a valve controlled outlet end portion316 which opposes a counter-recessed inlet end portion 318. Similarly,each of the flow passages 314 comprises a valve controlled outlet endportion 320 which opposes a counter-recessed inlet end portion 322.

To provide means for controlling the flow of damping between the upperand lower portions of the working chamber 42, two valve disks 324 and326 are provided. The valve disks 324 and 326 are coaxially arrangedadjacent the upper surface 304 and the lower surface 308 of the valvebody 302 respectively. The valve disk 324 is of a sufficient diameter soas to register with and cover the outlet end portions 316 of the flowpassages 312 thereby preventing damping fluid from entering the outletend portions 316. However, the valve disk 324 does not cover thecounter-recessed inlet end portions 322 of the flow passages 314 so asto allow damping fluid to enter the counter-recessed inlet end portions322. The valve disk 324 also cooperates with the recessed portion 306 onthe upper surface 304 of the valve body 302 so as to form a firstpressure chamber 328. Correlatively, the value disk 326 is of a diameterso as to register with and cover the outlet end portions 320 of the flowpassages 314 while not covering the counter-recessed inlet end portions322. In addition, the valve disk 326 cooperates with a second recessedportion 310 on the lower surface 308 on the valve body 302 to form asecond pressure chamber 330.

To support the valve body 302 within the pressure cylinder 40, the valvebody 302 has a central bore 332 operable to receive an axially extendingpiston post 334. The piston post 334 has an upper portion (not shown)with an internally threaded central bore adapted to threadably engage anexternally threaded lower end portion of the piston rod 46. An O-ring orsimilar sealing element 336 is disposed between the valve body 302 andthe piston post 334 to prevent damping fluid to flow therebetween. Tworadially extending flow passages 340 are disposed on the piston post 334which communicate with two flow passages 340 in the valve body 302 whichradially extend from the pressure chamber 328 to the central bore 332 ofthe valve body 302. In addition, the piston post 334 also has tworadially extending flow passages 346 which communicate with two flowpassages 348 which extend from the pressure chamber 330 to the centralbore 332 of the valve body 302. The flow passages 340-348 allow dampingfluid to flow between the pressure chambers 328 and 330 and one of thesolenoids described below. The piston post 334 further includes aradially extending step 349 having an outside diameter greater than thediameter of the central bore 332. Because the step 349 is disposed abovethe valve body 302, the step 349 limits upper movement of the valve body302 relative to the piston post 334. In addition, a piston retaining nut350 is provided having an internally threaded bore 352 which threadablyengages an externally threaded lower portion 354 of the piston post 334at a position below the valve body 302. Because the outside diameter ofthe piston retaining nut 350 is greater than the diameter of the centralbore 332 of the valve body 302, the nut 350 prevents downward movementof the valve body 302 relative to the piston post 334. The piston post334 and the piston retaining nut 350 also serve to secure the innermostportions of the valve disks 324 and 326. In this regard, the innermostportion of the valve disk 324 engages both the radially extending step349 of the piston post 334 and the upper surface 304 of the valve body302. In addition, the radially innermost portion of the valve disk 326engages the lower surface 308 of the valve body 302 and the pistonretaining nut 350.

To bias the valve disks 324 and 326 against the surfaces 304 and 308 ofthe valve body 302, a pair of coaxially arranged, axially spaced,helical coil springs 356 and 358 are provided. The spring 356 isdisposed coaxially with the piston post 334 between a radially extendingstep 360 formed on the piston post 334 and a backing plate 362 which islocated coaxially with, and adjacent to, the upper surface 304 of thevalve disk 324. Via the intermediate backing plate 362, the spring 356is able to resiliently and yieldably bias the valve disk 324 against theupper surface 304 of the valve body 302. Similarly, the spring 358 isdisposed between a radially extending flange 364 on the piston retainingnut 350 and a backing plate 366 which is located adjacent to, andcoaxially with, the valve disk 326. The spring 358 is thereby able toresiliently and yieldably biases the valve disk 326 against the surface308 of the valve body 302 by means of the intermediate backing plate366.

To provide an electrical controllable flow means operable to control theactuation of the valve disks 324 and 326, the piston 44 furthercomprises a first and second solenoid 370 and 372. The solenoid 370includes a housing 374 that is disposed within the central bore 375 ofthe piston post 334. Within the housing 374 are disposed a coil 376 andan armature 378 having enlarged counterbore 380. The armature 378 isaxially biased downward relative to the valve body 302 by a helical coilspring 382 which is disposed within the counterbore 380. The lower endof the spring 382 bears against the lower portion of the counterbore380, whereas the upper end of the spring 382 bears against the lowerside of a sealing plate 384. Similarly, the solenoid 372 also includes ahousing 386 which is coaxially disposed within the central bore 338 ofthe piston post 334 at a position below the solenoid 370. Within thehousing 386 is disposed a coil 388 and an armature 390 having anenlarged counterbore 392. The armature 390 is biased axially upwardrelative to the valve body 302 by a helical coil spring 394 which isdisposed within the counterbore 392. The upper end of the spring 394bears against the upper surface of the counterbore 392, whereas thelower end of the spring 394 bears against the upper surface of a sealingplate 396.

The axially lower end of the counterbore 380 of the solenoid 370 has anaxial flow passage 398 which is disposed coaxially with an axial flowpassage 400 in the housing 374. Similarly, the axially upper end of thecounterbore 392 of the solenoid 372 has an axially flow passage 402which is disposed coaxially with an axial flow passage 404 in thehousing 386. Because a pressure sensor 406 is disposed between thehousings 374 and 386 adjacent to the flow passages 400 and 404, thepressure sensor 406 is able to determine the pressure differentialbetween the damping fluid in the solenoid 370 and the damping fluid inthe solenoid 372. The output from the pressure sensor 406, together withthe output from an accelerometer 408, are delivered to the signalconditioning circuit 198 which amplifies the outputs prior to deliveryto the computer 202. The computer 202 then generates first and secondelectrical control signals for controlling the solenoids 370 and 372 viathe solenoid driving circuit 204.

The solenoid 370 operatively cooperates with the sealing plate 384 tocontrol the damping fluid between a central fluid passage 410 and aplurality of radially displaced passages 412 which are disposed on thesealing plate 384. When the solenoid 370 is open, damping fluid is ableto flow between the central fluid passage 410 and the radially displacedpassages 412. When the solenoid 370 is closed, the armature 378 movesdownwardly against the force of the spring 382 to a position and sealingengagement with the sealing plate 384. When this occurs, the armature378 prevents the flow of fluid between the passages 410 and 412.Similarly, the solenoid 372 cooperates with the sealing plate 396 tocontrol the damping fluid between a central fluid passage 414 and aplurality of radially displaced flow passages 416 which are disposed onthe sealing plate 396. When the solenoid 372 is open, damping fluid isable to flow between the central fluid passage 414 and the radiallydisplaced flow passages 416. When the solenoid 372 is closed, thearmature 390 moves downwardly against the force of the spring 394 to aposition in sealing engagement with the sealing plate 396. When thisoccurs, the armature 390 prevents the flow of fluid between the passages414 and 416.

The solenoid 370 communicates with the upper portion of the workingchamber 42 through an axial passage 422 and a radial passage 424 in thepiston post 334. The axial passage 422 extends from the central passage410 of the sealing plate 384 and communicates with the radial passage424 at its radially inwardmost end. In addition, the solenoid 372communicates with the lower portion of the working chamber 42 throughthe central bore 426 of a solenoid retaining plug 428. The solenoidretaining plug 428 has a threaded exterior surface which threadablyengages the lower portion of the piston post 334.

To allow the fluid flowing through the passages 410-418 to counterbiasthe valve disks 324 and 326, the valve body 302 further comprises theflow passages 430 and 432. The flow passage 430 radially extends fromthe pressure chamber 328 to the vertical flow passages 312, while theflow passage 432 extends from the pressure chamber 330 to the flowpassages 314. Accordingly, damping fluid in the flow passage 312 istherefore able to enter the pressure chamber 328 through the flowpassage 430, and damping fluid in the flow passages 314 is able to flowinto the pressure chamber 330 through the flow passage 432.

In accordance with the principles of the present invention, it will beseen that two flow paths are created in the valve body 302. The firstflow path allows damping fluid entering the flow passages 312 to flow tothe upper portion of the working chamber 42. In this regard, the firstflow path permits damping fluid in the vertical flow passages 312 toenter the pressure chamber 328 through the flow passage 430. The dampingfluid in the pressure chamber 328 then flows to the radially displacedflow passages 412 of the sealing plate 384 through the flow passage 342in the valve body 302 and the flow passage 340 in the piston post 334.If the solenoid 370 is open, damping fluid at the radially displacedflow passages 412 is able to flow through the second central flowpassage 410, the axial flow passage 422 and the radial flow passage 424to the upper portion of the working chamber 42.

The second flow path permits damping fluid flowing in the vertical flowpassage 314 to enter the lower portion of the working chamber 42. Inthis regard, the second flow path permits damping fluid in the flowpassages 314 to enter the pressure chamber 330 through the flow passage432. The damping fluid in the pressure chamber 330 is therefore able toflow to the radially displaced flow passages 416 in the sealing plate396 through the radially extended flow passage 346 in the valve body 302and the radially extending flow passage 348 in the piston post 334. Ifthe solenoid 372 is open, damping fluid delivered to the radiallydisplaced passages 416 of the sealing plate 396 is able to pass throughthe central fluid passage 314 to the lower portion of the workingchamber 42 through the central fluid passage 414 of the solenoid sealingplate 396.

To prevent leakage of damping fluid in the pressure chamber 328, anannular retaining seal 434 is provided. The annular retaining seal 434is disposed within the pressure chamber 328 adjacent to the valve disk324 so as to prevent damping fluid inside the pressure chamber 328 fromentering the upper portion of the working chamber 42. An annularretaining ring 436 is also disposed within the pressure chamber 328 toensure that the seal 434 is not displaced in such a manner as to allowhydraulic leakage between the pressure chamber 328 and the upper portionof the working chamber 42. In a similar fashion, an annular retainingseal 438 is disposed within the chamber 330 adjacent to the valve disk326. The annular retaining seal 438 is used to prevent damping fluidinside the pressure chamber 330 from entering the lower portion of theworking chamber 42. An annular retaining ring 440 is also disposedwithin the pressure chamber 330 to ensure that the seal 438 is notdisplaced in such a manner as to permit leakage of damping fluid betweenthe pressure chamber 330 and the lower portion of the working chamber42.

When a large amount of hydraulic fluid is to flow through the flowpassage 314 corresponding to a soft rebound stroke, the solenoid 372 isclosed thereby preventing fluid from flowing between the central fluidpassage 414 and the radially displaced passage 416 of the sealing plate396. Accordingly, damping fluid in the pressure chamber 328 is unable toflow into the lower portion of the working chamber 42. The pressure inthe pressure chamber 330 therefore increases which increases thecounter-biasing force applied to the valve disk 326. The valve disk 326is then deflected from the valve body 302 to a greater extent than wouldotherwise occur thereby increasing the flow of damping fluid through theflow passage 314. If a firm rebound stroke is desired, the solenoid 372is opened thereby causing the pressure in the pressure chamber 330 to besubstantially equal to the pressure inside the lower portion of theworking chamber 42. When this occurs, the counter-biasing force appliedto the valve disk 326 is reduced. Less damping fluid is therefore ableto flow through the flow passage 314 thereby producing a firm reboundstroke.

When a soft compression stroke is desired, the solenoid 370 is closedthereby preventing the flow of the damping fluid between the centralfluid passage 410 and the radially displaced fluid passage 412 in thesealing plate 384. Because fluid is not able to flow between thepassages 410 and 412, damping fluid in the pressure chamber 328 is notable to flow into the upper portion of the working chamber 42. Since thepressure of the damping fluid in the pressure chamber 328 becomesgreater than the pressure in the upper portion of the working chamber42, the counter-biasing force applied to the valve disk 324 increasescausing a greater deflection in the valve disk 324. This increase indeflection of the valve disk 324 increases the flow of damping fluidthrough the flow passage 312 thereby producing a soft compressionstroke. If a firm compression stroke is desired, the solenoid 370 isopened thereby connecting the pressure chamber 328 to the upper portionof the working chamber 42. Accordingly, the pressure inside the pressurechamber 328 is substantially equal to the pressure inside the upperportion of the working chamber 42, thereby limiting the counter-biasingforce applied to the valve disk 326.

In the third preferred embodiment of the present invention shown in FIG.16, a first and second annular valving members 442 and 444 are provided.The first and second annular valving members 442 and 444 are disposedcoaxially within the first pressure chamber 90 and the second pressurechamber 94 respectively. Two annular retaining seals 446 and 448 aredisposed between the first annular valving member 442 and the valve body66 to prevent hydraulic leakage therebetween. Similarly, two annularretaining seals 450 and 452 are disposed between the second annularvalving member 444 and the valve body 66 also to prevent hydraulicleakage. The first annular valving member 442 has an unloader port 454disposed between the first pressure chamber 90 and the upper portion ofthe working chamber 42. The unloader port 454 has an enlarged diameterportion 456 adjacent to the upper portion of the working chamber 42which may be used to receive a filter for filtering damping fluid. Inaddition, the unloader port 454 also has restricted diameter portion 458which is adjacent to the first pressure chamber 90. While the diameterof the enlarged diameter portion 456 may be 0.050 in and the restricteddiameter portion 458 may be 0.013 in, it is to be understood that othersuitable diameters may be used. The unloader port 454 functions in themanner similar to the flow passage 162 as described in connection withthe first preferred embodiment of the present invention.

In addition, the third preferred embodiment of the present invention hasa flow passage 460 which radially extends from the flow passage 105 tothe flow passage 160. The flow passage 460 functions in the mannersimilar to the flow passage 106 as shown in conjunction with the firstpreferred embodiment of the present invention.

In operation, the damping fluid flows into the flow passage 160 throughthe flow passage 460 depending on whether the solenoid 124 is open. Thedamping fluid in the flow passage 160 is then delivered to the firstpressure chamber 90 which is thereby able to bias the valve disk 72 toregulate the flow of damping fluid through the vertical flow passage 68.Because the restricted diameter portion 458 of the unloader port 454 isrelatively small, the pressure in the first pressure chamber 90 remainsrelatively constant during compression. During rebound, damping fluidfrom the upper portion of the working chamber 42 enters the firstpressure chamber 90 through the unloader port 454. The damping fluidentering the unloader port 452 is then able to flow from the firstpressure chamber 90 to the second pressure chamber 94 through the flowpassage 160. Depending on whether the solenoid 124 is open, dampingfluid is able to flow from the second pressure chamber 94 to the lowerportion of the working chamber 42 through the flow passages 460, 105,155, and 156, as well as the central bore 154 so that the pressure inthe second pressure chamber 94 may be regulated.

While it will be apparent that the preferred embodiments illustratedherein is well calculated to fill the objects stated above, it will beappreciated that the present invention is susceptible to modification,variation and change within departing from the scope of the invention.For example, a single computer may be used to control the dampingcharacteristics of several shock absorbers simultaneously. Otherprograms may also be used to control the damping characteristics of theautomobile 20, and the programs disclosed may be used individually orcollectively. In addition, the pressure sensor and the accelerometer mayboth be located within the solenoid housing. Further, the solenoid maybe replaced with other means for opening and closing the control flow tothe valves such as a piezoelectric closing element.

What is claimed is:
 1. A direct acting hydraulic shock absorber fordamping the movement of the body of an automobile comprising:a pressurecylinder forming a working chamber having first and second portionsoperable to store damping fluid; a piston disposed within said pressurecylinder between first and second portions of said pressure cylinder; apiston support member mechanically communicating with said piston; firstsensor means for determining the difference in pressure between thedamping fluid in said first and second portions of said working chamberso as to sense rebound and compression of said shock absorber, saidfirst sensor means operable to generate a first electrical signal inresponse to the difference in pressure between the damping fluid storedin said first and second portions, said first sensor means beingdisposed within said piston support member; second sensor means fordetermining the vertical velocity of the body of said automobile, saidsecond sensor means operable to generate a second electrical signal inresponse to the movement of the body of said automobile, said secondsensor means being disposed within said piston support member; means forgenerating an electrical control signal in electrical control signalbeing responsive to whether said shock absorber is in compression orrebound and whether the vertical velocity of the body of said automobileexceeds a predetermined value, and flow of damping fluid between saidfirst and second portions of said working chamber in response to saidelectrical control signal.
 2. The shock absorber as set forth in claim1, wherein said first sensor means comprises a pressure sensor having afirst surface communicating with the damping fluid stored in said firstportion of said working chamber, said pressure sensor further having asecond surface communicating with the damping fluid stored in saidsecond portion of said working chamber.
 3. The shock absorber as setforth in claim 1, wherein said second sensor means comprises anaccelerometer.
 4. The shock absorber set forth in claim 1, wherein saidelectrical controllable flow means comprises a solenoid, said solenoidoperable to regulate the flow of damping fluid between said first andsecond portions of said working chamber.
 5. A shock absorber of claim 4,wherein said means for generating said electrical control signalcomprises a signal conditioning circuit operable to amplify said firstand second electrical signals.
 6. The shock absorber of claim 5, whereinsaid means for generating an electrical control signal further comprisesa computer electrically communicating with said signal conditioningcircuit, said computer operable to generate an output in response to theoutput of said signal conditioning circuit.
 7. The shock absorber ofclaim 6, wherein said means for generating an electrical control signalfurther comprises a solenoid driving circuit operable to convert theoutput of said computer into said electrical control signal which may beused to energize said solenoid.
 8. The shock absorber of claim 7,wherein said solenoid driving circuit is operable to convert the outputof said signal conditioning circuit into said electrical control signalwhich may be used to energize said solenoid.
 9. A direct actinghydraulic shock absorber for damping the movement of the body of anautomobile comprising:a pressure cylinder forming a working chamberhaving first and second portions operable to store damping fluid; apiston disposed within said pressure cylinder between first and secondportions of said pressure cylinder; a piston support member mechanicallycommunicating with said piston; first sensor means for determining thedifference in pressure between the damping fluid in said first andsecond portions of said working chamber so as to sense rebound andcompression of said shock absorber, said first sensor means beingdisposed within said piston support member; second sensor means fordetermining the vertical velocity of the body of said automobile, saidsecond sensor means operable to generate a second electrical signal inresponse to the movement of the body of said automobile, said secondsensor means being disposed within said piston support member; means forgenerating first and second electrical control signals in response tosaid first and second electrical signals; first electrical controllableflow means for regulating the flow of damping fluid into said firstportion of said working chamber in response to said first electricalcontrol signal, said first electrical controllable flow means being atleast partially disposed within said piston; and second electricalcontrollable flow means for regulating the flow of damping fluid intosaid second portion of said working chamber in response to said secondelectrical control signal, said second electrical controllable flowmeans being at least partially disposed within said piston, said firstand second electrical controllable flow means being operable to regulatethe flow of damping fluid through said piston in response to whether thevertical velocity of the body of said automobile exceeds saidpredetermined value and whether said shock absorber is in compression orrebound.
 10. The shock absorber as set forth in claim 9, wherein saidfirst sensor means comprises a pressure sensor having a first surfacecommunicating with the damping fluid stored in said first portion ofsaid working chamber, said pressure sensor further having a secondsurface communicating with the damping fluid stored in said secondportion of said working chamber.
 11. The shock absorber as set forth inclaim 9, wherein said second sensor means comprises an accelerometer.12. The shock absorber set forth in claim 9, wherein said firstelectrical controllable flow means comprises a first solenoid, saidfirst solenoid operable to regulate the flow of damping fluid into saidfirst portion of said working chamber.
 13. The shock absorber set forthin claim 12, wherein said second electrical controllable flow meanscomprises a second solenoid, said second solenoid operable to regulatethe flow of damping fluid into said second portion of said workingchamber.
 14. The shock absorber as set forth in claim 13, wherein saidmeans for generating first and second electrical control signalscomprises a signal conditioning circuit operable to amplify the outputsfrom said first and second sensor means.
 15. The shock absorber as setforth in claim 14, wherein said means for generating first and secondelectrical control signals further comprises a computer electricallycommunicating with said signal conditioning circuit, said computeroperable to generate an output in response to the output from saidsignal conditioning circuit.
 16. The shock absorber as set forth inclaim 15, wherein said means for generating first and second electricalcontrol signals further comprises a solenoid driving circuit operable toconvert the output from said computer into voltage levels which may beused to energize said first and second solenoids.
 17. The shock absorberof claim 16, wherein said solenoid driving circuit being furtheroperable to convert the output from said signal conditioning circuitinto an output which may be used to energize said first and secondsolenoids.
 18. A method for regulating the flow of damping fluid betweenfirst and second portions of the working chamber of a direct actinghydraulic shock absorber disposed between the sprung and unsprungportions of a vehicle, said shock absorber having a piston disposedbetween said first and second portions of said working chamber and apiston support member mechanically communicating with said piston, saidmethod comprising the steps of:sensing the pressure differential betweensaid first and second portions of said working chamber to determinewhether said shock absorber is in compression or rebound, said step ofsensing the pressure differential including the step of recording theoutput of first sensor means disposed within said piston support member;sensing the vertical movement of the sprung portion of said vehicle byrecording the output of second sensor means disposed within said pistonsupport member; determining whether the vertical velocity of the body ofsaid automobile exceeds a predetermined value; regulating the flowdamping fluid between said first and second portions of said workingchamber through said piston in response to whether the vertical velocityof the body of said automobile exceeds a predetermined value and whethersaid shock absorber is in compression or rebound.
 19. The method ofclaim 18, wherein said step of sensing the pressure differential betweensaid first and second portions comprises the step of recording theoutput of a pressure sensor in fluid communication with said first andsecond portions of said working chamber.
 20. The method of claim 19,wherein said step of sensing the vertical movement of the sprung portionof said vehicle comprises the step of recording the output from anaccelerometer.
 21. The method of claim 20, wherein said step ofregulating the flow of damping fluid between said first and secondportions of said working chamber comprises the step of deliveringdamping fluid from said first and second portions to an electricalcontrollable flow means for regulating the flow of damping fluid betweensaid first and second portions of said working chamber.
 22. The methodof claim 21, wherein said electrical controllable flow means comprises asolenoid, said solenoid operable to regulate the flow of damping fluidbetween said first and second portions of said working chamber.
 23. Themethod of claim 22, wherein said step of regulating the flow of dampingfluid between said first and second portions of said working chambercomprises the step of delivering the outputs from said pressure sensorand said accelerometer to a signal conditioning circuit operable toamplify the outputs from said pressure sensor and said accelerometer.24. The method of claim 23, wherein said step of regulating the flow ofdamping fluid between said first and second portions of said workingchamber further comprises the step of delivering the output of saidsignal conditioning circuit to a computer electrically communicatingwith said signal conditioning circuit, said computer operable togenerate an output in response to the output of said signal conditioningcircuit.
 25. The method of claim 24, wherein said step of regulating theflow of damping fluid between said first and second portions of saidworking chamber further comprises the step of delivering the output fromsaid computer to a solenoid driving circuit operable to convert theoutput of said computer into voltage levels which may be used toenergize said solenoid.
 26. The method of claim 25, wherein said step ofregulating the flow of damping fluid between said first and secondportions of said working chamber further comprises the step ofdelivering the output from said signal conditioning circuit to saidsolenoid driving circuit operable to convert the output from said signalconditioning circuit into voltage levels which may be used to energizesaid solenoid.
 27. A method for regulating the flow of damping fluidbetween first and second portions of the working chamber of a directacting hydraulic shock absorber disposed between the sprung and unsprungportions of the vehicle, said shock absorber having a piston disposedbetween said first and second portions of said working chamber and apiston support member mechanically communicating with said piston, saidmethod comprising the steps of:sensing the pressure differential betweensaid first and second portions of said working chamber to determinewhether said shock absorber is in compression or rebound, said step ofsensing the pressure differential including the step of recording theoutput of first sensor means disposed within said piston support member;sensing the vertical movement of the sprung portion of said vehicle byrecording the output of second sensor means disposed within said pistonsupport member; determining whether the vertical velocity of the body ofsaid automobile exceeds a predetermined value; regulating the flow ofdamping fluid into said first portion of said working chamber by a firstelectrical controllable flow means for regulating the flow of dampingfluid into said first portion of said working chamber; and regulatingthe flow of damping fluid into said second portion of said workingchamber by a second electrical controllable flow means for regulatingthe flow of damping fluid into said second portion of said workingchamber, said first and second electrical controllable flow means beingoperable to regulate the flow of damping fluid through said piston inresponse to whether the vertical velocity of the body of said automobileexceeds said predetermined value and whether said shock absorber is incompression or rebound.
 28. The method of claim 27, wherein said step ofsensing the pressure differential between said first and second portionscomprises the step of recording the output from a pressure sensor influid communicating with said first and second portions of said workingchamber, said pressure sensor operable to sense the pressuredifferential between the damping fluid in said first and second portionsof said working chamber.
 29. The method of claim 28, wherein said stepof sensing the vertical movement of the sprung portion of said vehiclecomprises the step of recording the output of an accelerometer.
 30. Themethod of claim 29, wherein said first electrical controllable flowmeans comprises a first solenoid, said first solenoid operable toregulate the flow of damping fluid into said first portion of saidworking chamber.
 31. The method of claim 30, wherein said secondelectrical controllable flow means comprises a second solenoid, saidsecond solenoid operable to regulate the flow of damping fluid into saidsecond portion of said working chamber.
 32. The method of claim 31,wherein said step of regulating the flow of damping fluid into saidfirst portion of said working chamber comprises the step of deliveringthe output from said pressure sensor and said accelerometer to a signalconditioning circuit operable to amplify the outputs from said pressuresensor and said accelerometer.
 33. The method of claim 32, wherein saidstep of regulating the flow of damping fluid into said first portion ofsaid working chamber further comprises the step of delivering the outputfrom said signal conditioning circuit to a computer electricallycommunicating with said signal conditioning circuit, said computeroperable to generate an output inresponse to the output of said signalconditioning circuit.
 34. The method of claim 33, wherein said step ofregulating the flow of damping fluid into said first portion of saidworking chamber further comprises the step of delivering the output ofsaid computer to a solenoid driving circuit operable to convert theoutput of said computer into voltage levels which may be used toenergize said first solenoid.
 35. The method of claim 34, wherein saidsolenoid driving circuit being further operable to convert the output ofsaid signal conditioning circuit into an output which may be used toenergize said first solenoid.
 36. The method of claim 35, wherein saidsolenoid driving being further operable to convert the output of saidcomputer into voltage levels which may be used to energize said secondsolenoid.
 37. The method of claim 36, wherein said solenoid drivingcircuit being further operable to convert the output of said signalconditioning circuit into an output which may be used to energize saidsecond solenoid.
 38. A shock absorber for damping the movement of thebody of an automobile relative to a wheel of said automobile, said shockabsorber having a pressure cylinder with a reciprocating piston disposedtherein operable to divide the working chamber formed by said pressurecylinder into first and second portions, said piston mechanicallycommunicating with a piston support member, said shock absorbercomprising:first valve means for controlling the flow of damping fluidbetween said first and second portions of said working chamber duringcompression; second valve means for controlling the flow of dampingfluid between said first and second portions of said working chamberduring rebound; first sensor means for determining the difference inpressure between said first and second portions of said working chamberso as to sense rebound and compression, said first sensor means beingdisposed within said piston support member; second sensor means fordetermining the vertical velocity of the body of said automobile, saidsecond sensor means being disposed within said piston support member;electrical controllable flow means operable to control the actuation ofsaid first and second valve means; a first flow path between said firstand second portions of said working chamber through said electricalcontrollable flow means; a second flow path between said second portionof said working chamber and said first valve means through saidelectrically controllable flow means; and means for controllablyactuating said electrical controllable flow means being operable toregulate the flow of damping fluid through said piston in response towhether the vertical velocity of the body of said automobile exceedssaid predetermined value and whether said shock absorber is incompression or rebound.
 39. The shock absorber of claim 38, wherein saidpiston support member comprises an axially extending piston rodmechanically communicating with an end fitting, said end fittingoperably securing said piston rod to said body of said automobile, saidpiston being secured to said piston rod by a piston post fixedly securedto said piston rod.
 40. The shock absorber of claim 39, wherein saidpiston rod has an externally threaded end portion adopted to threadablyengage an internally threaded central bore portion of said piston post.41. The shock absorber of claim 39, wherein said piston has a centralbore operable to receive said piston post.
 42. The shock absorber ofclaim 39, wherein said piston post comprises a radially extending stepportion, said shock absorber further comprising a first spring disposedbetween said step portion of said piston post and said first valvemeans, said first spring operable to bias said first valve means againstsaid piston.
 43. The shock absorber of claim 42, wherein said shockabsorber further comprises a piston retaining nut operable to securesaid piston to said piston post, said piston retaining nut having aninternally threaded central bore operable to threadably engage anexternal threaded end portion of said piston post.
 44. The shockabsorber of claim 43, further comprising a second spring disposedbetween a radially extending flange on said piston retaining nut andsaid second valve means, said second spring means operable to bias saidsecond valve means against said piston.
 45. The shock absorber of claim44, wherein said piston comprises a valve body having a first surfaceperpendicular to the axis of reciprocation of said piston, said firstsurface having a first recessed portion.
 46. The shock absorber of claim45, wherein said valve body further comprises a second surfaceperpendicular to the axis of reciprocation of said piston, said firstsurface having a second recess portion.
 47. The shock absorber of claim46, wherein said first recess portion and said first valve means areoperable to form a first pressure chamber, said first valve meansoperable to increase the flow of damping fluid between said first andsecond portions of said working chamber during compression of said shockabsorber when said pressure in said first pressure chamber exceeds thepressure in said first portion of said working chamber.
 48. The shockabsorber of claim 47, further comprising a first sealing elementdisposed within said first pressure chamber, said first sealing elementbeing operable to prevent damping fluid in said first pressure chamberto flow into said first portion of said working chamber.
 49. The shockabsorber of claim 48, further comprising a first annular retaining ringdisposed within said first pressure chamber, said first annularretaining ring being operable to prevent displacement of said firstsealing element with respect to said first valve means.
 50. The shockabsorber of claim 47, wherein said second recess portion and said secondvalve means are operable to form a second pressure chamber, said secondvalve means operable to increase the flow of damping fluid between saidfirst and second portions of said working chamber during rebound of saidshock absorber when said pressure in said first pressure chamber exceedsthe pressure in the second portion of said working chamber.
 51. Theshock absorber of claim 50, further comprising a second sealing elementdisposed within said second pressure chamber, said second sealingelement operable to prevent damping fluid in said second pressurechamber to flow into said second portion of said working chamber. 52.The shock absorber of claim 51, further comprising a second annularretaining ring disposed within said second pressure chamber, said secondannular retaining ring operable to prevent displacement of said secondsealing element with respect to said second valve means.
 53. The shockabsorber of claim 47, wherein said electrical controllable flow meanscomprises a solenoid.
 54. The apparatus of claim 53, wherein saidsolenoid comprises a sealing plate having a central flow passage and aplurality of radially displaced flow passages, said central flow passagebeing in fluid communication with said second portion of said workingchamber and said radially displaced flow passages being in fluidcommunication with said second pressure chamber.
 55. The shock absorberof claim 54, wherein said solenoid further comprises an armatureoperable to engage said sealing plate when said solenoid is closed. 56.The shock absorber of claim 55, wherein said armature is operable toprevent the flow of damping fluid between said central flow passage andsaid radially displaced flow passages when said solenoid is closed. 57.The shock absorber of claim 56, wherein said solenoid further comprisesa spring operable to bias said armature in a direction opposing saidsealing plate.
 58. The shock absorber of claim 57, wherein said armaturehas a central bore operable to permit damping fluid from said secondportion of said working chamber to flow therethrough.
 59. The shockabsorber of claim 58, wherein said solenoid further comprises a solenoidhousing and a housing cap, said housing cap having an axial flow passagein fluid communication with said central bore of said armature.
 60. Theshock absorber of claim 59, wherein said piston further comprises anannular member disposed within said piston post between said piston rodand said solenoid housing.
 61. The shock absorber of claim 60, whereinsaid annular member has an axial flow passage and a radially extendingflow passage, said radially extending flow passage permitting fluidcommunication between the first portion of said working chamber and saidaxial flow passage through a flow passage in said piston post.
 62. Theshock absorber of claim 61, wherein said pressure sensor has a firstsurface communicating with said axial flow passage of said annularmember, said pressure sensor having a second surface in fluidcommunication with the axial flow passage in said housing cap.
 63. Theshock absorber of claim 62, wherein said valve body comprises a firstplurality of vertical flow passages operatively associated with saidfirst and second valve means to permit damping fluid to flow from saidfirst portion of said working chamber to said second portion of saidworking chamber when the pressure of the damping fluid in said firstportion of said working chamber is greater than the pressure of thedamping fluid in said second portion.
 64. The shock absorber of claim63, wherein said valve body comprises a second plurality of verticalflow passages, said second plurality of vertical flow passagesoperatively associated with said first and second valve means to permitdamping fluid to flow from said second portion of said working chamberto said first portion when the pressure of the damping fluid in saidsecond portion is greater than the pressure of the damping fluid in saidfirst portion.
 65. The shock absorber of claim 64, wherein said firstflow path comprises a flow passage between one of said second pluralityof vertical flow passages in said valve body and said second pressurechamber, said first flow path further comprising a flow passage in saidvalve body mating with a flow passage in said piston post operable toallow damping fluid in said second pressure chamber to flow into saidradially displaced flow passages in said sealing plate.
 66. The shockabsorber of claim 65, wherein said first flow path further comprisessaid radially displaced flow passages in said sealing plate.
 67. Theshock absorber of claim 66, wherein said second flow path comprises aflow passage between said first pressure chamber and said secondpressure chamber, said second flow path further comprising said flowpassage in said valve body mating with a flow passage in said pistonpost.
 68. The shock absorber of claim 67, wherein said second flow pathfurther comprises said radially displaced flow passages in said sealingplate.
 69. The direct acting shock absorber for damping the movement ofthe body of an automobile comprising:a pressure cylinder forming aworking chamber with first and second portions operable to store dampingfluid; a piston disposed within said pressure cylinder between saidfirst and second portions of said working chamber, said piston in fluidcommunicating with said second portion of said working chamber; meansfor supporting said piston within said pressure cylinder, said means forsupporting said piston being in fluid communication communicating withsaid first portion of said working chamber; first sensor means fordetermining the difference in the pressure between the damping fluid insaid first and second portions of said working chamber so as to senserebound and compression, said first sensor means operable to generatefirst electrical signal in response to the difference in pressurebetween the damping fluid stored in said first and second portions, saidfirst sensor means being disposed within said means for supporting saidpiston; second sensor means for determining the vertical velocity of thebody of said automobile, said second sensor means operable to generate asecond electrical signal in response to the movement of the body of saidautomobile, said first sensor means being disposed within said means forsupporting said piston; means for generating electrical control signalin response to said first and second electrical signals, said electricalcontrol signal being responsive to whether said shock absorber is incompression or rebound and to whether the vertical velocity of the bodyof said automobile exceeds a predetermined value; and electricalcontrollable flow means for regulating the flow of damping fluid betweensaid first and second portions of said working chamber through saidpiston in response to said electrical control signal.
 70. The shockabsorber of claim 69, wherein said means for supporting said pistoncomprises a piston post with a central bore, said piston post having aflow passage between said first portion of said working chamber and saidcentral bore.
 71. The shock absorber of claim 70, wherein said apparatusfurther comprises an annular member disposed within said piston post,said annular member having a flow passage in fluid communication withfirst flow passage in said piston post and said first sensor means. 72.The shock absorber of claim 71, wherein said first sensor means being inmechanical communication with said annular member.
 73. The shockabsorber of claim 72, wherein said electrical controllable flow meansincludes a flow passage in fluid communication with the second portionof said working chamber, said first sensor means in fluid communicationwith said flow passage in said electrical controllable flow means.
 74. Ashock absorber for damping the movement of the body of an automobile,said shock absorber having a piston supported by a piston supportmember, said shock absorber comprising:a pressure cylinder forming aworking chamber having first and second portions operable to storedamping fluid; first sensor means for determining the difference inpressure between the damping fluid in said first and second portions ofsaid working chamber, said first sensor means operable to generate afirst electrical signal in response to whether the shock absorber is incompression or rebound, said first sensor means being disposed withinsaid support member; second sensor means for determining movement of thebody of said automobile, said second sensor means operable to generate asecond electrical signal in response to the vertical movement of thebody of said automobile, said first sensor means being disposed withinsaid piston support member; means for generating an electrical controlsignal in response to said first and second electrical signals, saidmeans for generating an electrical control signal operable to record theoutput of said first sensor means and determine whether said shockabsorber is in compression or rebound, said means for generating anelectrical control signal being further operable to determine whetherthe vertical velocity of the body of said automobile exceeds apredetermined value; first electrical controllable flow means forregulating the flow of damping fluid between said first and secondportions of said working chamber through said piston, said firstelectrical controllable flow means disposed within said pressurecylinder and being operable to regulate the flow of damping fluid duringcompression of said shock absorber; and second electrical controllableflow means for electrically regulating the flow of damping fluid betweensaid first and second portions of said working chamber through saidpiston in response to said electrical control signal, said secondelectrical controllable flow means disposed within said pressurecylinder and being operable to regulate the flow of damping fluid duringthe rebound of said shock absorber.
 75. The shock absorber of claim 74,wherein said first electrical controllable flow means comprises a firstsolenoid, said first solenoid operable to regulate the flow of dampingfluid into said first portion of said working chamber.
 76. The shockabsorber of claim 75, wherein said second electrical controllable flowmeans further comprises a second solenoid, said second solenoid operableto regulate the flow of damping fluid into said second portion of saidworking chamber.
 77. The shock absorber of claim 76, wherein said meansfor generating an electrical control signal comprises signalconditioning circuit operable to amplify the outputs from said first andsecond sensor means.
 78. The shock absorber of claim 77, wherein saidmeans for generating an electrical control signal comprises a computer,said computer operable to generate an output in response to the outputof said signal conditioning circuit.
 79. The shock absorber of claim 78,wherein said means for generating an electrical control signal furthercomprises a solenoid driving circuit operable to convert the output ofsaid computer into voltage levels which may be used to energize saidfirst solenoid.
 80. The shock absorber of claim 79, wherein saidsolenoid driving circuit is further operable to convert the output ofsaid signal conditioning circuit into an output which may be used toenergize said first solenoid.
 81. The shock absorber of claim 80,wherein said solenoid driving circuit is further operable to convert theoutput of said computer into voltage levels which may be used toenergize said second solenoid.
 82. The shock absorber of claim 81,wherein said solenoid driving circuit is further operable to convert theoutput of said signal conditioning circuit into an output which may beused to energize said second solenoid.
 83. The shock absorber of claim74, wherein said shock absorber further comprises a valve body and afirst and a second valve disk biased against opposing surfaces of saidvalve body, said valve body having a first plurality of vertical flowpassages operatively associated with said first and second valve disksto permit damping fluid to flow from said first position of said workingchamber to said second portion of said working chamber when the pressureof the damping fluid in said first portion of said working chamber isgreater than the pressure of the damping fluid in said second portion.84. The shock absorber of claim 83, wherein said valve body furthercomprises a second plurality of vertical flow passages, said secondplurality of vertical flow passages operatively associated with saidfirst and second valve disks to permit damping fluid to flow from saidsecond portion of said working chamber to said first portion of saidworking chamber when the pressure of the damping fluid in said secondportion is greater than the pressure of the damping fluid in said firstportion.
 85. The shock absorber of claim 84, wherein said valve bodyfurther comprises a first recessed portion cooperating with said firstvalve disk to create a first pressure chamber, said first solenoidoperable to selectively increase the pressure inside said first pressurechamber so as to create a pressure differential on opposing sides ofsaid first valve disk.
 86. The shock absorber of claim 85, wherein saidvalve body further comprises a second recessed portion cooperating withsaid second valve disk to create a second pressure chamber, said secondsolenoid operable to selectively increase the pressure inside saidsecond pressure chamber so as to create a pressure differential onopposing sides of said second valve disk.
 87. The shock absorber ofclaim 86, wherein said first solenoid permits selective fluidcommunication between said first pressure chamber and said first portionof said working chamber when said solenoid is open.
 88. The shockabsorber of claim 87, wherein said second solenoid permits selectivefluid communication between said second pressure chamber and said secondportion of said working chamber.
 89. The shock absorber of claim 88,wherein said first plurality of vertical flow passages is in fluidcommunication with said first pressure chamber.
 90. The shock absorberof claim 89, wherein said second plurality of vertical flow passages isin fluid communication with said second pressure chamber.
 91. A methodfor regulating the flow of damping fluid through a piston disposedbetween the first and second portions of the working chamber of thedirect acting shock absorber, said piston being supported in saidworking chamber by a piston support member, said shock absorber operableto damp movement of the body of an automobile, said method comprisingthe steps of:recording the output of a first sensor means fordetermining the difference in pressure between the damping fluid in saidfirst and second portions of said working chamber so as to determinewhether said shock absorber is in compression or rebound, said firstsensor means operable to generate a first electrical signal in responseto the difference in pressure between the damping fluid stored in saidfirst and second portions of said working chamber, said first sensormeans being disposed within said piston support member; recording theoutput of a second sensor means for determining the vertical velocity ofa body of said automobile, said second sensor means operable to generatea second electrical signal in response to the movement of the body ofsaid automobile, said second sensor means being disposed within saidpiston support member; generating an electrical control signal inresponse to said first and second electrical signals, said electricalcontrol signal being responsive to whether said shock absorber is incompression or rebound and to whether the vertical velocity of the bodyof said automobile exceeds a predetermined value; and regulating theflow of damping fluid through said piston by an electrical controllableflow means in response to said electrical control signal.
 92. The methodof claim 91, wherein said first sensor means comprises a pressure sensorhaving a first surface communicating with a damping fluid stored in saidfirst portion of said working chamber, said pressure sensor furtherhaving a second surface communicating with the damping fluid stored insaid second portion of said working chamber.
 93. The method of claim 91,wherein said second sensor means comprises an accelerometer.
 94. Themethod of claim 91, wherein said electrical controllable flow meanscomprises a solenoid, said solenoid operable to regulate the flow ofdamping fluid between said first and second portions of said workingchamber.
 95. The method of claim 91, wherein said piston comprises avalve body and a first and a second valve disk biased against opposingsurfaces of said valve body, said valve body having a first plurality ofvertical flow passages operatively associated with said first and secondvalve disks to permit damping fluid to flow from said first portion ofsaid working chamber to said second portion of said working chamber whenthe pressure of the damping fluid in said first portion of said workingchamber is greater than the pressure of the damping fluid in said secondportion.
 96. The method of claim 95, wherein said valve body comprises asecond plurality of vertical flow passages, said second plurality ofvertical flow passages operatively associated with said first and secondvalve disks to permit damping fluid to flow from said second portion ofsaid working chamber to said first portion of said working chamber whenthe pressure of the damping fluid in said second portion is greater thanthe pressure of the damping fluid in said first portion.
 97. The methodof claim 96, wherein said electrical controllable flow comprises asolenoid, said solenoid is operable to selectively create a pressuredifferential on opposing sides of said first valve disk therebycounter-biasing said first valve disk.
 98. The method of claim 97,wherein said solenoid is further operable to selectively create apressure differential on opposing sides of said second valve diskthereby counter-biasing said second valve disk.
 99. The method of claim98, wherein said valve body further comprises a first recessed portioncooperating with said first valve disk to create a first pressurechamber, said solenoid operable to selectively increase the pressureinside said first pressure chamber so as to create a pressuredifferential on opposing sides of said first valve disk.
 100. The methodof claim 99, wherein said valve body further comprises a second recessedportion cooperating with said second valve disk to create a secondpressure chamber, said solenoid operable to selectively increase thepressure inside said second pressure chamber so as to create a pressuredifferential on opposing sides of said second valve disk.
 101. Themethod of claim 100, wherein said shock absorber further comprises apiston post operable to support said valve body.
 102. The method ofclaim 101, wherein said solenoid further comprises a sealing plate, saidsealing plate having a central flow passage and a plurality of radiallydisplaced flow passages, said central flow passage being in fluidcommunication with said second portion of said working chamber, saidradially displaced flow passages being in fluid communication with saidsecond pressure chamber through a flow passage in said valve body and aflow passage in said piston post.
 103. The method of claim 102, whereinsaid first pressure chamber is in fluid communication with said secondpressure chamber.
 104. The method of claim 103, wherein said secondpressure chamber is in fluid communication with at least one of saidsecond plurality of vertical flow passages.
 105. The method of claim104, wherein said solenoid further comprises an armature operable toengage said sealing plate when said solenoid is closed.
 106. The methodof claim 105, wherein said armature is operable to prevent the flow ofdamping fluid between said central flow passage and said radiallydisplaced flow passages when said solenoid is closed.
 107. The method ofclaim 106, wherein said solenoid further comprises a spring is operableto bias said armature in a direction away from said sealing plate. 108.The method of claim 107, wherein said armature has a central boreoperable to permit damping fluid from said second portion of saidworking chamber to flow therethrough.
 109. The method of claim 108,wherein said solenoid further comprises a solenoid housing and a housingcap, said housing cap having an axial flow passage in fluidcommunication with said central bore of said armature.
 110. The methodof claim 109, wherein said piston further comprises an annular memberdisposed within said piston post between said piston rod and saidsolenoid housing.
 111. The method of claim 110, wherein said annularmember has an axial flow passage and a radially extending flow passage,said radially extending flow passage permitting fluid communicationbetween the first portion of said working chamber and said axial flowpassage through a flow passage in said piston post.
 112. The method ofclaim 111, wherein said hock absorber further comprises a pressuresensor, said pressure sensor having a first surface communicating withsaid axial flow passage of said annular member, said pressure sensorhaving a second surface in fluid communication with said axial flowpassage in said housing cap.
 113. The method of claim 112, furthercomprising an accelerometer disposed on said annular member.
 114. Amethod for regulating the flow of damping fluid between the first andsecond portions of a direct acting shock absorber, said shock absorberable to damp movement between the body and a wheel of an automobile,said method comprising the steps of:determining whether the frequency ofthe vertical movement of the body of said automobile is substantiallyequal to a first predetermined value; determining whether the frequencyof the vertical movement of the wheel of said automobile issubstantially equal to a second predetermined value by sensing thedifference in pressure between the damping fluid in said first andsecond portions of said working chamber; and regulating the flow ofdamping fluid through a piston disposed between said first and secondportions of said working chamber in response to whether the frequency ofthe body of said automobile is substantially equal to a firstpredetermined value and whether the frequency of vertical movement ofthe wheel of said automobile is substantially equal to a secondpredetermined value.
 115. The method of claim 114, wherein said step ofdetermining whether the frequency of the vertical movement of the bodyof said automobile is substantially equal to said first predeterminedvalue comprises the step of integrating the output of an accelerometerwhich moves in unison with the body of said automobile.
 116. The methodof claim 114, wherein said step of determining whether the frequency ofthe vertical movement of the wheel of said automobile is substantiallyequal to said second predetermined value comprises the step of recordingthe pressure differential between said first and second portions of saidworking chamber and calculating the value of A² according to thefollowing equation: ##EQU2## where: P_(t) is the differential pressurebetween the upper portion and the lower portion of said working chamberat time t; andT is the period of the natural frequency of the wheel ofsaid automobile.
 117. A method for regulating the flow of damping fluidbetween the first and second portions of a working chamber of a directacting shock absorber during compression and rebound, said shockabsorber operable to damp the movement of the body of an automobile,said method comprising the steps of:recording the output of a pressuresensor disposed between the first and second portions of said workingchamber to determine whether said shock absorber is in compression orrebound; sensing the vertical movement of the body of said automobile;determining whether the vertical velocity of the body of said automobileexceeds a predetermined value; and regulating the flow of damping fluidthrough a piston disposed between said first and second portions of saidworking chamber in response to whether the vertical velocity of the bodyof said automobile exceeds said predetermined value and whether saidshock absorber is in compression or rebound.
 118. The method of claim117, wherein the step of determining whether the vertical velocity ofthe body of said automobile exceeds said predetermined value comprisesthe step of integrating the output of an accelerometer, saidaccelerometer operable to sense the vertical acceleration of the body ofsaid automobile.
 119. The method of claim 117, wherein said step ofregulating the flow of damping fluid comprises the step of increasingthe flow of damping fluid between said first and second portion of saidworking chamber during both compression and rebound when the magnitudeof the vertical velocity of the body of said automobile is below saidpredetermined value.
 120. The method of claim 119, wherein said step ofregulating the flow of damping fluid comprises the step of increasingthe flow of damping fluid between said first and second portions of saidworking chamber during rebound and decreasing the flow duringcompression when the vertical velocity of the body of said automobile isdownward and the magnitude of said vertical velocity exceeds saidpredetermined value.
 121. The method of claim 120, wherein said step ofregulating the flow of damping fluid comprises the step of decreasingthe flow of damping fluid between said first and second portions duringrebound and increasing the flow during compression when the verticalvelocity of the body of said automobile is upward and the magnitude ofsaid vertical velocity exceeds said predetermined value.
 122. A methodfor regulating the flow of damping fluid between first and secondportions of the working chamber of a direct acting shock absorber havinga piston disposed therein, said shock absorber operable to damp themovement of the body of an automobile, said method comprises;recordingthe output of a pressure sensor disposed between said first and secondportions of said working chamber; determining whether said shockabsorber is in compression or rebound by using the output of saidpressure sensor; determining the vertical velocity of said pistondisposed within said shock absorber; and determining whether thevertical velocity of said piston exceeds a predetermined value; andregulating the flow of damping fluid between said first and secondportions of said working chamber in response to the vertical velocity ofsaid piston and whether said shock absorber is in compression orrebound.
 123. The method of claim 121, wherein said step of regulatingthe flow of damping fluid between said first and second portions of saidworking chamber comprises the step of decreasing the flow of dampingfluid between said first and second portions during compression when themagnitude of the vertical velocity of said piston exceeds saidpredetermined value.
 124. The method of claim 123, wherein said step ofregulating the flow of damping fluid between said first and secondportions comprises the step of decreasing the flow of damping fluidbetween said first and second portions when the magnitude of thevertical velocity of said piston exceeds said predetermined value. 125.A method for regulating the flow of damping fluid between first andsecond portions of a working chamber of a shock absorber, said shockabsorber operable to damp movement of the body and a wheel of anautomobile, said method comprising the steps of:recording the output ofa pressure sensor disposed between said first and second portions ofsaid working chamber during a predetermined length of time; calculatingthe value of A² according to the following equation: ##EQU3## where:P_(t) is the differential pressure between the first and second portionsof said working chamber at time t; T is the period of the naturalfrequency of the wheel of said automobile; and decreasing the flow ofdamping fluid between said first and second portions of said workingchamber during compression of said shock absorber when the value of A²exceeds a predetermined value.
 126. The method of claim 125, furthercomprising the additional step of decreasing the flow of damping fluidbetween said first and second portions of said working chamber duringrebound of said shock absorber when the value of A² exceeds saidpredetermined value.
 127. A method for regulating the flow of dampingfluid through a piston disposed between first and second portions of theworking chamber of a direct acting hydraulic shock absorber, said pistonbeing supported by a piston support member, said shock absorber beingdisposed between the sprung and unsprung portions of an automobile, saidmethod comprising the steps of:sensing the pressure differential betweensaid first and second portions of said working chamber so as to permitdetermination of whether said shock absorber is in compression orrebound by recording the output of first sensor means disposed withinsaid piston support member; sensing the vertical movement of the sprungportion of said vehicle by recording the output of second sensor meansdisposed within said piston support member; determining whether thevertical velocity of the body of said automobile exceeds a predeterminedvalue; regulating the flow of damping fluid into said first portion ofsaid working chamber by a first electrical controllable flow means forregulating the flow of damping fluid into said first portion of saidworking chamber; and regulating the flow of damping fluid into saidsecond portion of said working chamber by a second electricalcontrollable flow means operable to regulate the flow of damping fluidinto said second portion of said working chamber, said first and secondelectrical controllable flow means being operable to regulate the flowof damping fluid through said piston in response to whether the verticalvelocity of the body of said automobile exceeds said predetermined valueand whether said shock absorber is in compression or rebound.
 128. Themethod of claim 127, wherein said step of sensing the pressuredifferential between said first and second portions of said workingchamber comprises the step of recording the output from a pressuresensor disposed between said first and second portions of said workingchamber, said pressure sensor operable to sense the pressuredifferential between the damping fluid in said first and second portionsof said working chamber.
 129. The method of claim 127, wherein said stepof sensing the vertical velocity of the sprung portion of said vehiclecomprises the step of recording the output of an accelerometer disposedwithin said shock absorber.
 130. The method of claim 127, wherein saidfirst electrical controllable flow means comprises a first solenoid,said first solenoid operable to regulate the flow of damping fluid intosaid first portion of said working chamber.
 131. The method of claim130, wherein said second electrical controllable flow means furthercomprises a second solenoid, said second solenoid operable to regulatethe flow of damping fluid into said second portion of said workingchamber.
 132. The method of claim 131, wherein said step of regulatingthe flow of damping fluid into said first portion of said workingchamber comprises the step of delivering the output from said pressuresensor and said accelerometer to a signal conditioning circuit operableto amplify the outputs from said pressure sensor and said accelerometer.133. The method of claim 132, wherein said step of regulating the flowof damping fluid into said first portion of said working chamber furthercomprises the step of delivering the output from said signalconditioning circuit to a computer electrically communicating with saidsignal conditioning circuit, said computer operable to generate anoutput in response to the output of said signal conditioning circuit.134. The method of claim 133, wherein said step of regulating the flowof damping fluid into said first portion of said working chamber furthercomprises the step of delivering the output of said computer to asolenoid driving circuit operable to convert the output of said computerinto voltage levels which may be used to energize said first solenoid.135. The method of claim 134, wherein said solenoid driving circuit isfurther operable to convert the output of said signal conditioningcircuit into an output which may be used to energize said firstsolenoid.
 136. The method of claim 135, wherein said solenoid driving isfurther operable to convert the output of said computer into voltagelevels which may be used to energize said second solenoid.
 137. Themethod of claim 136, wherein said solenoid driving circuit is furtheroperable to convert the output of said signal conditioning circuit intoan output which may be used to energize said second solenoid.
 138. Themethod of claim 132, wherein said piston comprises a valve body and afirst and a second valve disk biased against opposing surfaces of saidvalve body, said valve body having a first plurality of vertical flowpassages operatively associated with said first and second valve disksto permit damping fluid to flow from said first portion of said workingchamber to said second portion of said working chamber when the pressureof the damping fluid in said first portion of said working chamber isgreater than the pressure of the damping fluid in said second portion.139. The method of claim 138, wherein said valve body comprises a secondplurality of vertical flow passages, said second plurality of verticalflow passages operatively associated with said first and second valvedisks to permit damping fluid to flow from said second portion of saidworking chamber to said first portion of said working chamber when thepressure of the damping fluid in said second portion is greater than thepressure of the damping fluid in said first portion.
 140. The method ofclaim 139, wherein said valve body further comprises a first recessesportion cooperating with said first valve disk to create a firstpressure chamber, said first solenoid operable to selectively increasethe pressure inside said first pressure chamber so as to create apressure differential on opposing sides of said first valve disk. 141.The method of claim 140, wherein said valve body further comprises asecond recessed portion cooperating with said second valve disk tocreate a second pressure chamber, said second solenoid operable toselectively increase the pressure inside said second pressure chamber soas to create a pressure differential on opposing sides of said secondvalve disk.
 142. The method of claim 141, wherein said first solenoidpermits selective fluid communication between said first pressurechamber and said first portion of said working chamber when saidsolenoid is open.
 143. The method of claim 142, wherein said secondsolenoid permits selective fluid communication between said secondpressure chamber and said second portion of said working chamber. 144.The method of claim 143, wherein said first plurality of vertical flowpassages is in fluid communication with said first pressure chamber.145. The method of claim 144, wherein said second plurality of verticalflow passages is in fluid communication with said second pressurechamber.